From: Gobind (gobind@inbox.com)
Date: Wed Feb 21 2007 - 05:43:00 ART
OK,I got it but as said that priority would be multiples of 4096,so there is certain limit,I mean multiples of 4096 upto certain value? Also Scoot,the p;d way for Bridge ID (16 bit proirity +MAC) isnt used now a days(or some use it now a days also?)?
So it would be like this:-
Multiples of 4096+Vlan Id (like 10 for Vlan 10)
Right? Or I am misunderstanding the concept of Vlan ID/System Ext Id,as far I am thinking and got to know from gus(correct me if I am wrong,but bit confused):-
Sys Ext=Vlan Id=Vlan Number
Gobind
> -----Original Message-----
> From: swm@emanon.com
> Sent: Tue, 20 Feb 2007 19:39:37 -0500
> To: louisccie_r_s@yahoo.com, gobind@inbox.com, ccielab@groupstudy.com
> Subject: RE: Bridge Priority
>
> I think you'd have to sit there with a lot of math to verify that, but
> it's
> not accurate anyway, so save yourself some time. :)
>
> The old way for Bridge ID was 16-bit priority + MAC address = 64 bits.
>
> Now, the bridge ID is still 64 bits, but instead of having 16 bits for
> priority (who has 65000 switches anyway?), there are 4 bits used for
> priority and then 12 bits used for VLAN ID. So that's why you can get
> some
> strange values.
>
> So the priority field is still 16 bits:
>
> ppppvvvvvvvvvvvv
>
> Where p = priority and v = vlan ID.
>
> HTH,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
> #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPexpert VP - Curriculum Development
> IPexpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Lou
> Ioanni
> Sent: Tuesday, February 20, 2007 5:28 PM
> To: Gobind; ccielab@groupstudy.com
> Subject: Re: Bridge Priority
>
> Right. You do not deduct vlan number from default to get priority. What
> confused you is the way they map vlans to priorities ex. 2-32768, 3-4094,
> etc
>
> I never heard of such formula. I will be very surprised if there is
> any.
>
> Loizos Y.
> CCIE#10702 R & S
>
> Gobind <gobind@inbox.com> wrote:
> So in no case this is true,right?:-
>
> Bridge priority = Default bridge priority - Vlan Number
>
> I heard it in CBT was got confused!
>
>> -----Original Message-----
>> From: louisccie_r_s@yahoo.com
>> Sent: Tue, 20 Feb 2007 11:21:11 -0800 (PST)
>> To: gobind@inbox.com, ccielab@groupstudy.com
>> Subject: Re: Bridge Priority
>>
>> Yes each vlan has its own root depending on the priority. If
>> priorities are the same then it uses the mac to select the root. Each
>> vlan and priorities are combined to create a unique ID. Check the
>> floowing link for a siminlar question and answers:
>>
>> http://www.velocityreviews.com/forums/t37177-bridge-priority-and-sysid
>> ext-number.html
>>
>> Gobind wrote: If the sys-id-ext usually correlates to Vlan Number,it
>> means like for Vlan Number 1 the sys-id-ext would be 1,right? it is
>> taken automatically or manually? I am confused about the part that the
>> If in a switch every Vlan has its own priority then when the Root
>> Election occurs,does it occurs to every Vlan,lets say there are
>> 3 Vlans and what if it have different Priority then is it also
>> possible that on Switch would be Root Bridge for 1 Vlan and not other
>> two(due to higher Priority)?
>>
>>
>> -----Original Message-----
>> From: louisccie_r_s@yahoo.com
>> Sent: Tue, 20 Feb 2007 10:59:29 -0800 (PST)
>> To: gobind@inbox.com, ccielab@groupstudy.com
>> Subject: Re: Bridge Priority
>>
>>
>> I am not sure if you refering to a specific lab exercise, but in real
>> environments you can select which switch you want to be the Root
>> Bridge for specific vlans by lowering the priority from the default
>> 32768. The lower the priority the more prefered to be the root
>> (example 32000). If you want to FORCE a specific switch to be the root
>> then you set priority 0. For example:
>>
>> spanning-tree vlan 10-14 priority 0 (This will set this switch to be
>> the root for vlans 10,11,12,13,14)
>>
>> You can set a different root bridge for each group of vlans for load
>> balancing. You can direct certain vlans traffic through one
>> distribution switch and other vlans through the other distribution
>> reduntant switch for load balancing L2 traffic.
>>
>> Usually is good to set the L3 distribution switches as the Root
>> bridges for the vlans attached to the access layer switches attached to
> it.
>>
>> Thanks,
>>
>> Loizos Y.
>> CCIE#10702 R & S
>>
>>
>>
>> Gobind wrote: Hi Guys,
>>
>> I have some confusion wiht the Bridge Priority.In Some CBTs I am
>> getting to hear that:-
>>
>> Bridge Priority is Default Priority(32768) - Vlan Number
>>
>> I asked my friend,he said Default Priority is Default Priority + Vlan
>> Number
>>
>> In one Cisco Dumentation it is written:-
>>
>> "Each VLAN on each network device has a unique 64-bit bridge ID
>> consisting of a bridge priority value, an extended system ID, and an
>> STP MAC address allocation"
>>
>> Source:- http://www.cisco.com/en/U
>> S/products/hw/switches/ps708/products_configuration_guide_chapter09186
>> a008016
>> 0a5b.html#wp1040218
>>
>> I am really confused(maybe I am getting it wrong) what Priority(in STP
>> is),also I am not getting if the Priority is Default priority + Vlan
>> Number or - Vlan Number then what Vlan Number is it refering to? I
>> mean the Trunk belongs to every Vlan then which Vlan Number it takes
>> while making the election.(when it sends BPDU i.e.)
>>
>> Gobind
>>
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